1. Field of the Invention
The present invention relates to a ligating instrument for use on the tip end of an endoscope for ligating a plurality of varices such as enlarged and tortuous veins that occur in an esophagus or any of other cavities in the body of a patient.
2. Description of the Prior Art
One known endoscopic ligating instrument is disclosed in U.S. Pat. No. 4,735,194. The disclosed endoscopic ligating instrument has an outer tube mounted on the tip end of an endoscope and an inner tube axially movably inserted in the outer tube. A trip wire has an end coupled to the inner tube, extends through a biopsy channel, and has an opposite end projecting out of the endoscope and joined to a handle. When the handle is pulled, the trip wire is axially moved to move the inner tube rearwardly into the outer tube. A ligating O-ring made of an elastomeric material is expanded radially outwardly and mounted on a tip end of the inner tube which projects out of the front end of the outer tube.
The endoscopic ligating instrument is used as follows: The endoscope is inserted into the esophagus, for example, of a patient until the tip end of the inner tube covers a varix to be ligated. Then, after a region where the varix exists is drawn into the inner tube under suction or the like, the handle is pulled to move the inner tube rearwardly into the outer tube. The ligating O-ring is now pushed off the inner tube by the tip end of the outer tube, and contracted radially inwardly, thereby ligating the base of the target lesion. Since the blood flow to the ligated varix is blocked, the ligated varix hardened and removed. The removal of the ligated varix finishes the treatment of the patient.
However, since only one ligating O-ring is mounted on the inner tube, if a plurality of varices are to be ligated successively, then it is necessary, each time a varix has been removed, to take the endoscope out of the cavity, replace the inner tube with a new inner tube with a ligating O-ring mounted thereon, and then insert the endoscope back into the cavity for ligating treatment. For ligating a plurality of varices, therefore, the endoscope is required to be inserted into and taken out of the cavity as many times as the number of varices to be ligated. Such a ligating practice has caused considerable pain to the patient.